Managers of systems that use steam as an energy source need to calculate the true cost of generating steam to prepare budgets and optimise their management of resources. You can use different ways to calculate the cost of steam depending on several factors, including the production stage, the methods used and the type of steam generated. However, calculating the overall cost is a matter of simple arithmetic if you have access to the necessary data.
Calculate the cost of fuel. This factor usually is the most expensive component. To calculate, multiply the price of fuel by the difference between the enthalpy of the steam generated and the enthalpy of the boiler's feed water. Enthalpy is a measure of the heat added or lost in a system and is measured by the energy required to produce 450 g (1 lb) of saturated steam, or BTU (British thermal unit).
Divide the result by 100 and divide again by the boiler's efficiency. The efficiency of a boiler depends on the method the machine uses to generate steam. For instance, natural gas boilers have an efficiency of 0.817, or 81.7 per cent, while a coal boiler has a combustion efficiency of 87.6 per cent, or 0.876.
Add the price of the water supply and of treating the boiler feed water.
Add the cost of providing the energy to pump the water and run the air fan. These expenses depend on the current cost of electricity and the efficiency of the pumps and fans the system uses.
Add the charges for disposing of the water, sewer charges and the ash generated by the boiler.
Include the value of the filters, cleanup, health and safety and other environmental emissions control measures.
Add the cost of materials and labour required to keep up the maintenance of the boiler and auxiliary steam generating systems.
- A shortcut method to estimate the overall cost of steam is to multiply the cost of fuel, calculated in Step 1, by 1.3. However, this method only applies for larger facilities. Smaller generators may be less efficient and use more than 130 per cent of the cost of fuel.